A vehicle-mounted air conditioner is required to meet space savings because various pieces of equipment are housed in the engine room of a vehicle. For this reason, in recent years there have been provided integrated electric compressors in which a compressor that constitutes a vehicle-mounted air conditioner, a motor for driving the compressor and a driving board for driving the motor are housed integrally in a housing.
In such an integrated electric compressor, switching elements composed of a plurality of IGBTs (insulated gate bipolar transistors) are provided on a board for controlling the operation of a motor in order to supply a three-phase alternating current to the motor. A high voltage, such as 300 V, is supplied to these switching elements from an external high-voltage power source (not shown) (refer to Patent Document 1, for example).    Patent Document 1: Japanese Patent No. 3760887
Package parts of commercial IGBTs have hitherto been used in such switching elements. Package parts of IGBTs are units and in each unit one IGBT and one diode that constitute one switching element are modularized.
Such units generate a three-phase current to operate a motor. For this reason, the units are provided with the IGBTs and the diodes in quantities of three sets corresponding to the U-phase, V-phase and W-phase.
Incidentally, miniaturization is constantly required of each automotive accessory. This applies also to the electric compressor, and in studying the miniaturization of the electric compressor, the miniaturization of a control board for driving the motor becomes essential.
However, when package parts are used in the switching elements as previously, the package parts have sizes that are large to a certain degree. For this reason, if the switching elements are provided in quantities of three sets as described above, the size of a board on which the switching elements are mounted increases. Then, the board may sometimes protrude sideways from the electric compressor. Therefore, it may be possible to prevent the board from protruding sideways from the electric compressor by dividing the board into a plurality of layers. In this concept, however, the thickness of the control board increases virtually and, therefore, it cannot be said that this is an adequate solution from the standpoint of miniaturization.
In addition, the control board includes parts that generate heat, such as IGBTs. Because of the heat radiation from these parts, these parts are preferably disposed along the portion of the housing in which the refrigerant flows so that these parts are cooled by a refrigerant flowing in the housing of the electric compressor. However, because the arrangement of the parts is limited by this, it is difficult to miniaturize the control board also in this respect.
The present invention has been made on the basis of such a technical challenge, and has as its object the provision of an integrated electric compressor that enables a control board to be miniaturized while ensuring a layout in which the heat radiation of parts is considered.